Here is a 5-day full-body strength training workout plan that you can perform at the gym for 30 minutes each day. This plan incorporates compound exercises that work multiple muscle groups at once, allowing you to maximize your time and effort in the gym.

Day 1: Upper Body Push

1. Bench Press: 3 sets of 8-10 reps

2. Overhead Press: 3 sets of 8-10 reps

3. Push-ups: 3 sets of 10-12 reps

4. Tricep Dips: 3 sets of 10-12 reps

5. Dumbbell Flyes: 3 sets of 10-12 reps

Day 2: Lower Body

1. Squats: 3 sets of 8-10 reps

2. Deadlifts: 3 sets of 8-10 reps

3. Lunges: 3 sets of 10-12 reps per leg

4. Leg Press: 3 sets of 10-12 reps

5. Calf Raises: 3 sets of 10-12 reps

Day 3: Upper Body Pull

1. Pull-ups or Lat Pulldowns: 3 sets of 8-10 reps

2. Bent-Over Rows: 3 sets of 8-10 reps

3. Seated Cable Rows: 3 sets of 10-12 reps

4. Bicep Curls: 3 sets of 10-12 reps

5. Hammer Curls: 3 sets of 10-12 reps

Day 4: Core and Cardio

1. Plank: 3 sets of 30-60 seconds

2. Russian Twists: 3 sets of 10-12 reps per side

3. Bicycle Crunches: 3 sets of 10-12 reps per side

4. Mountain Climbers: 3 sets of 10-12 reps per side

5. Jumping Jacks: 3 sets of 30-60 seconds

Day 5: Full Body Circuit

Perform each exercise back-to-back with minimal rest between exercises. Rest for 1-2 minutes between circuits. Aim to complete 3-4 circuits.

1. Squats: 10-12 reps

2. Push-ups: 10-12 reps

3. Lunges: 10-12 reps per leg

4. Bent-Over Rows: 10-12 reps

5. Overhead Press: 10-12 reps

Remember to warm up before each workout with 5-10 minutes of light cardio and dynamic stretches. Additionally, focus on proper form and technique for each exercise to prevent injuries and maximize results. It's also important to gradually increase the weight or intensity as you progress to challenge your muscles and promote strength gains.

Please note that this workout plan is a general guideline and may need to be adjusted based on your individual fitness level, goals, and any specific needs or limitations you may have. It's always a good idea to consult with a certified personal trainer or fitness professional to tailor a workout plan specifically for you.

References:

- American Council on Exercise (ACE): https://www.acefitness.org/education-and-resources/lifestyle/exercise-library/

- National Strength and Conditioning Association (NSCA): https://www.nsca.com/education/articles/ptq/the_basics_of_strength_training_program_design/